Maybe you can find out if anyone is a vegetarian ahead of time. If there is you could make a small casserole without meat and add extra beans for protein. Then I would make a green salad, taco chips and salsa and brownies. Keep it simple, that's the purpose of the casserole. I'm a vegetarian and I do not expect there to be food I can eat at any event I go it. I usually take a protein bar or my own food because I don't want to inconvenience anyone.